U.S. patent application number 11/452144 was filed with the patent office on 2006-10-19 for implantable device using ultra-nanocrystalline diamond.
Invention is credited to Robert J. Greenberg, Brian V. Mech.
Application Number | 20060235475 11/452144 |
Document ID | / |
Family ID | 26716503 |
Filed Date | 2006-10-19 |
United States Patent
Application |
20060235475 |
Kind Code |
A1 |
Mech; Brian V. ; et
al. |
October 19, 2006 |
Implantable device using ultra-nanocrystalline diamond
Abstract
An implantable biocompatible device, that may be either a sensor
or stimulator, having electronic circuitry and electrodes formed on
a substrate, is uniformly covered with a coating approximately
one-micron thick of ultra-nanocrystalline diamond, hermetically
sealing the electronic circuitry. Selected electrodes are either
left uncovered during coating or uncovered by conventional
patterning techniques, allowing the electrodes to be exposed to
living tissue and fluids. The ultra-nanocrystalline diamond coating
may be doped to create electrically conductive electrodes. These
approaches eliminate the need for a hermetically sealed lid or
cover to protect hybrid electronic circuitry, and thus allow the
device to be thinner than otherwise possible. The conformal
ultra-nanocrystalline diamond coating uniformly covers the device,
providing relief from sharp edges and producing a strong, uniformly
thick hermetic coating around sharp edges and on high aspect-ratio
parts.
Inventors: |
Mech; Brian V.; (Sherman
Oaks, CA) ; Greenberg; Robert J.; (Los Angeles,
CA) |
Correspondence
Address: |
SECOND SIGHT MEDICAL PRODUCTS, INC.
12744 SAN FERNANDO ROAD
BUILDING 3
SYLMAR
CA
91342
US
|
Family ID: |
26716503 |
Appl. No.: |
11/452144 |
Filed: |
June 12, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10039842 |
Oct 26, 2001 |
|
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11452144 |
Jun 12, 2006 |
|
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60272962 |
Feb 28, 2001 |
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Current U.S.
Class: |
607/2 ;
623/6.63 |
Current CPC
Class: |
H01L 2924/0002 20130101;
A61K 9/0009 20130101; A61N 1/36046 20130101; C23C 16/278 20130101;
C23C 16/274 20130101; H01L 23/3107 20130101; C23C 16/277 20130101;
A61N 1/0543 20130101; H01L 23/29 20130101; C23C 16/279 20130101;
H01L 2924/0002 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
607/002 ;
623/006.63 |
International
Class: |
A61N 1/375 20060101
A61N001/375 |
Claims
1. A biocompatible device comprising: a device for implantation in
living tissue; a thin film of ultra-nanocrystalline diamond
deposited on said biocompatible device wherein said thin film forms
at least a portion of a biocompatible hermetically sealed
package.
2. The biocompatible device of claim 1 wherein said biocompatible
device is comprised of one or more subassemblies which are coated
with ultra-nanocrystalline diamond to achieve a biocompatible
hermetically sealed package.
3. The biocompatible device according to claim 1 wherein said
biocompatible device comprises an electronic device.
4. The biocompatible device according to claim 3 wherein said
biocompatible device comprises a magnet.
5. The biocompatible device of claim 3 wherein said biocompatible
device is at least partially coated with an ultra-nanocrystalline
diamond film that comprises an electrical insulator.
6. The biocompatible device of claim 3 wherein said biocompatible
device is at least partially coated with an ultra-nanocrystalline
diamond film that comprises an electrical conductor.
7. The biocompatible device according to claim 3 wherein said thin
film is doped to provide for electrical conductivity.
8. The biocompatible device according to claim 7 wherein a thin
film of ultra-nanocrystalline diamond is doped to form one or more
electrodes, where one or more electrodes are an integral part of
said thin film, for communicating electrical signals with living
tissue.
9. The biocompatible device according to claim 7 wherein said
doping is selective, forming electric conductivity in some
locations and electrical insulation in other locations.
10. The biocompatible device according to claim 3 wherein an
integrated circuit comprises a sensor.
11. The biocompatible device according to claim 3 wherein said
integrated circuit comprises a stimulator.
12. The biocompatible device according to claim 11 wherein a
stimulator comprises a retinal electrode array prosthesis.
13. The biocompatible device according to claim 1 wherein said
biocompatible device comprises an electrically conducting wire.
14. The biocompatible device according to claim 13 wherein said
electrically conducting wire comprises a coil.
15. The biocompatible device according to claim 1 wherein said
ultra-nanocrystalline diamond coating is approximately constant in
thickness over uneven portions of said device to provide a smooth
coating with rounded edges.
16. The biocompatible device according to claim 1 wherein said
ultra-nanocrystalline diamond coating is patterned by
photolithography.
17. The biocompatible device according to claim 1 wherein said
ultra-nanocrystalline diamond coating is patterned by selective
seeding.
18. The biocompatible device according to claim 1 wherein said
ultra-nanocrystalline diamond coating is patterned by oxygen
etching.
19. The biocompatible device according to claim 1 wherein said
ultra-nanocrystalline diamond forms a capacitive relationship with
living tissue that is in close proximity to said biocompatible
device.
20. A method of hermetically sealing an implantable biocompatible
device comprising: providing an implantable biocompatible device;
depositing a thin film coating of ultra-nanocrystalline diamond on
said implantable biocompatible device forming a biocompatible,
hermetic seal.
21. The method according to claim 20 wherein said step of
depositing said thin film coating includes depositing said thin
film coating in a constant thickness to provide for a smooth
rounded package.
22. The method according to claim 20 further comprising the step of
patterning said thin film by photolithography.
23. The method according to claim 20 further comprising the step of
patterning said thin film coating by selective seeding.
24. The method according to claim 20 further comprising the step of
patterning said thin film coating by oxygen etching.
25. The method according to claim 20 further comprising the step of
doping said thin film coating to provide for electrical
connectivity.
26. The method according to claim 25 wherein said step of doping is
selective, providing for electrical conductivity in some locations
and electrical insulation in other locations.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/039,842, filed Oct. 26, 2001, which claims the benefit
of U.S. Provisional Application No. 60/272,962, filed Feb. 28, 2001
and which is related to U.S. patent application Ser. No.
10/046,458, filed Oct. 26, 2001 and is hereby incorporated by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to an implantable device that
communicates with living tissue, wherein electronic circuitry
associated with the implantable device is coated with a thin film
that is biocompatible and hermetic.
BACKGROUND OF THE INVENTION
[0003] Hermetic electrically insulating materials are desirable for
packaging of electronics in implantable stimulating and sensing
devices, where implantation is in living tissue in a living body.
The implanted devices must be biocompatible. The devices must not
only exhibit the ability to resist the aggressive environment
present in the body, but must also be compatible with both the
living tissue and with the other materials of construction for the
device itself. The materials are selected to avoid both galvanic
and electrolytic corrosion. Typical materials of construction for
implantable devices include ceramics, plastics, or metals. The
ceramics may be glass, or a metal oxide, such as alumina, titania,
zirconia, stabilized-zirconia, partially-stabilized zirconia,
tetragonal zirconia, magnesia-stabilized zirconia, ceria-stabilized
zirconia, yttria-stabilized zirconia, or calcia-stabilized
zirconia, or yttria-stabilized zirconia, although other ceramic
materials may also be used. The plastics may be epoxy,
polycarbonate, or plexiglass. Typical metals include titanium or
titanium alloy (such as Ti-6 Al-4 V), although other metals, such
as platinum, iridium, platinum-iridium, stainless steel, tantalum,
niobium, or zirconium may be used.
[0004] One solution to achieving biocompatibility, hermeticity, and
galvanic and electrolytic compatibility for an implanted device is
to encase the device in a protective environment. It is well known
to encase implantable devices with glass or with a case of ceramic
or metal. Schulman, et al. (U.S. Pat. No. 5,750,926) is one example
of this technique. It is also known to use alumina as a case
material for an implanted device as disclosed in U.S. Pat. No.
4,991,582. These cases are often too thick for use with miniature
implantable devices, such as the prosthetic retinal implants of
Second Sight, LLP. The case unacceptably increases the size of the
device and becomes a limiting factor as to where the devices may be
placed in the body.
[0005] It is also known to protect an implantable device with a
thin layer or layers of an electrically insulating, protective
material, as disclosed by Schulman, et al. (U.S. Pat. No.
6,043,437). Coatings of alumina, zirconia, or other ceramic, less
than 25 microns thick, were applied by evaporative coating, vapor
deposition, or ion-beam deposition.
[0006] Disadvantageously, the sensor described in the referenced
patent and patent applications is relatively thick. For some
applications, where small size is required, such as when a device
is placed in an eye, eyelid, or in a fingertip, space is very
limited and only a very small device will fit. There remains a need
for yet a smaller sensor or a stimulator that performs all of the
same functions as the prior apparatus, i.e., that provides working
electrodes exposed to living tissue, perhaps with a selected enzyme
placed over one electrode, and with hermetically-sealed electronic
circuitry controlling the stimulator or sensor and communicating
with other internal or external devices. The present invention
advantageously addresses these and other needs.
[0007] U.S. Pat. No. 5,660,163 discloses an implantable glucose
sensor that is fabricated on a ceramic substrate. Working
electrodes and other elements associated with the sensor are
exposed to a conductive fluid contained within a reservoir or inner
sheath that covers the substrate. An outer sheath is also placed
over the sensor, with a window formed over one of the working
electrodes. A selected enzyme, such as glucose oxidate, is placed
within the window. As disclosed in U.S. Pat. No. 5,660,163, five
wires or conductors are attached to the electrodes and connected to
electronic circuitry, e.g., a circuit such as is shown in FIG. 3 of
the '163. U.S. Pat. No. 5,660,163 is incorporated herein by
reference.
[0008] Additional features, aspects, and improvements of a glucose
sensor of the type disclosed in U.S. Pat. No. 5,660,163 are further
disclosed in U.S. Pat. No. 6,081,736; U.S. Pat. No. 6,119,028; and
U.S. Pat. No. 5,999,848; each of which above-referenced patent
applications is incorporated herein by reference.
SUMMARY OF THE INVENTION
[0009] The implantable biocompatible device of the instant
invention is coated with a thin film of ultra-nanocrystalline
diamond. The device is generally an integrated circuit chip that
contains electronic circuitry for communicating with living tissue.
The biocompatible device may be either an implanted stimulator or a
sensor of living tissue function. An ultra-nanocrystalline diamond
thin film coating assures that the device will be biocompatible and
hermetically sealed. Ultra-nanocrystalline diamond may be pattered
by conventional methods, including photolithography, seeding, and
oxygen etching, to expose electrodes to the living tissue. Further,
the ultra-nanocrystalline diamond may be doped, by a variety of
known methods, to create an electrically conductive area that acts
as an electrode, which may in turn contact living tissue to be a
stimulator or a sensor. The ultra-nanocrystalline diamond coating
provides a conformal coating on the biocompatible device, which is
of approximately uniform thickness around sharp corners and on high
aspect-ratio parts. The conformal nature of the coating helps
assure hermeticity and strength despite the presence of difficult
to coat shapes.
OBJECTS OF THE INVENTION
[0010] It is an object of the invention to provide an
ultra-nanocrystalline diamond coated device that is hermetically
sealed and biocompatible for implantation in a living body.
[0011] It is an object of the invention to provide an
ultra-nanocrystalline diamond coated device that is has a uniform
thickness coating around corners such that the coating maintains
its hermetic sealing capability.
[0012] It is an object of the invention to provide an electrically
insulating ultra-nanocrystalline diamond coated integrated circuit
wherein the coating is patternable via conventional techniques to
reveal electrodes.
[0013] It is an object of the invention to provide an
ultra-nanocrystalline diamond coated integrated circuit wherein the
coating contains openings to reveal electrodes.
[0014] It is an object of the invention to provide an electrically
insulating ultra-nanocrystalline diamond coated integrated circuit
wherein the coating is patterned by selective doping to yield
integral electrodes.
[0015] It is an object of the invention to provide an implantable
device, including electrodes and electronic circuitry that does not
require a lid or cover for hermetically sealing hybrid electronic
circuitry.
[0016] Other objects, advantages and novel features of the present
invention will become apparent from the following detailed
description of the invention when considered in conjunction with
the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 illustrates a cross-sectional view of the integrated
circuit coated with ultra-nanocrystalline diamond.
[0018] FIG. 2 depicts a cross-sectional view of an integrated
circuit having a conductive portion of the ultra-nanocrystalline
diamond coating.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] Ultra-nanocrystalline diamond (UNCD) thin film coatings
exhibit excellent mechanical, electrical, and electrochemical
properties. Using a thin film coating deposition process, such as
that disclosed by Gruen and Krauss (U.S. Pat. No. 5,772,760) yields
a coating that is inherently low in porosity, electrically
non-conductive and biocompatible. Coatings as thin as 40 nm have
demonstrated excellent hermetic properties. UNCD thin film coatings
are conformal when applied to complex or high aspect-ratio shapes.
Since UNCD can be either patterned or selectively deposited, it
also permits exposure of conductors and/or vias for interconnection
with other components.
[0020] Characteristics of this UNCD coating that make it
particularly well suited to the present invention are:
[0021] uniform morphology resulting in a very high bulk
density,
[0022] highly conformal and able to cover very high-aspect ratio
features uniformly,
[0023] electrical properties can be controlled by varying the
deposition parameters, so as to make selected areas electrically
conductivity,
[0024] low-temperature deposition thereby avoiding damage to
electrical and passive components, and
[0025] easily patternable via selective seeding, photolithography,
or oxygen etching.
[0026] UNCD coating properties are not all present in any other
single coating candidate for microchip packaging. Alternative
coatings are conventional chemical vapor deposited diamond thin
films, diamond-like carbon, or SiC. UNCD coatings exhibit:
[0027] (a) extremely low surface roughness (20-30 nm),
approximately independent of film thickness up to approximately 10
.mu.m thickness;
[0028] (b) extremely good conformality when deposited on high
aspect-ratio features;
[0029] (c) extremely low coefficient of friction;
[0030] (d) high hardness, fracture toughness, flexural strength,
and wear life,
[0031] (e) low electrical conductivity, but can be doped to become
conductive, and
[0032] (f) excellent resistant to degradation in living tissue
environments.
[0033] The UNCD coating consists primarily of phase pure randomly
oriented diamond crystallites. UNCD coatings are grown using a
microwave plasma chemical vapor deposition technique involving a
C.sub.60/Ar or CH.sub.4/Ar chemistry, which provides C.sub.2 dimers
as the main growth species that insert directly into the growing
diamond lattice with a low energy barrier. The limited amount of
atomic hydrogen in the plasma leads to a very high re-nucleation
rate (.about.10.sup.11 cm.sup.-2 sec.sup.-1). This results in UNCD
coatings with 2 to 5 nm grain size and 0.4 nm grain boundaries that
provide the unique properties described herein. In addition, the
low activation energy for C.sub.2 species incorporation into the
growing film yields UNCD films at temperatures as low as
approximately 350.degree. C. This temperature is very low compared
to that required by many conventional coating processes, such as
glass encapsulation or chemical vapor deposition.
[0034] The present invention uses the "chip" of an integrated
circuit chip (which contains desired electronic circuitry) as the
substrate for the stimulator or sensor, with the substrate and
electronic circuitry being covered, as required, with a protective
UNCD coating. Such approach advantageously eliminates the need for
a hermetically sealed lid or cover, and thus allows the stimulator
or sensor to be made much thinner than has heretofore been
possible.
[0035] Integrated circuits that are implanted in a living body
benefit from a UNCD coating that, in addition to biocompatibility,
corrosion resistance, and hermeticity, can be patterned to expose
the electrodes.
[0036] A UNCD protective coating covers the substrate, hermetically
sealing the circuitry under the coating. Electrodes associated with
the implantable device may be selectively left uncovered by the
protective coating, thereby allowing such electrodes to be exposed
to body tissue and fluids when the stimulator is implanted in
living tissue. The exposed electrodes must be biocompatible. To
this end, the electrodes may be plated with a biocompatible metal,
such as platinum or iridium or alloys of platinum and/or
iridium.
[0037] Alternately, using any of several patterning techniques that
are well known in the art, it is possible to expose selected
electrical contacts by selectively removing portions of the UNCD
coating. There are several known permutations and combinations of
process steps that can lead to this result.
[0038] Also, the UNCD coating itself may be selectively doped so as
to create electrically conductive integral portions of the coating
that then act as electrodes, which in turn contact the living
tissue.
[0039] The inert nature of a very thin coating of UNCD was
demonstrated by the present inventors. A silicon substrate coated
with 40 nm of UNCD film was exposed to silicon etchant having a
composition of 67% HNO.sub.3 and 33% HF, by volume. The etchant was
placed drop-wise on the UNCD film, where it was allowed to stand at
60.degree. C. for one-hour. The coating had been unaffected when
observed microscopically at 1000.times. after this exposure.
[0040] Therefore, the UNCD film coating may be used as part of a
hermetic chip level packaging process to isolate implantable
electronic and passive components from chemical or electrolytic
attack in the body.
[0041] The UNCD coating on an integrated circuit is "conformal",
which means that the coating has a uniform thickness as the coating
follows the contours of the device. Achieving a conformal coating
on high aspect-ratio parts and around sharp corners on these
devices is a particular challenge for thin films that are deposited
by other means.
[0042] In accordance with another aspect of the invention, an
efficient integral capacitor may be formed between the stimulator
and the living tissue by virtue of depositing a very thin layer of
UNCD insulating film on the surface of the stimulator such that the
thin film causes a capacitor to be formed. Such a capacitor can
advantageously be used to effectively stop current flow to the
living tissue, thereby avoiding harm to the tissue that is caused
by electrical current flow, while allowing the stimulating voltage
signal to pass to the tissue.
[0043] The invention may further be characterized as a method of
making an implantable device that is either a stimulator or a
sensor, where the device includes a substrate, electrodes formed on
the substrate, and electrical circuitry formed on the substrate.
Such method includes the steps of: (a) forming the electrical
circuitry on the surface of a semiconductor substrate; (b) forming
electrodes on the semiconductor substrate; (c) electrically
interconnecting the electrodes with the electrical circuitry
through the use of conductive paths that pass through or on the
body of the semiconductor substrate; and (d) depositing a
protective coating of UNCD over the entire surface area of the
substrate, except for select areas of the electrodes, so that all
but the exposed area of the electrodes is sealed and protected.
[0044] FIG. 1 provides a cross-sectional view of a preferred
embodiment of a coated integrated circuit 1. Due to the extremely
thin film that is required, these figures are not drawn to scale.
The integrated circuit is shown, where the silicon substrate 3
contains an electrode 5 on one surface that is connected by metal
trace 7 to active circuitry 9. The silicon substrate 3 is coated
with an ultra-nanocrystalline diamond 11. The ultra-nanocrystalline
diamond 11 coating has been removed in a selected portion to expose
electrode 5 such that electrode 5 can contact living tissue
directly when implanted. The ultra-nanocrystalline diamond 11 has
an approximately uniform thickness and has rounded corners 13 which
are formed as part of the normal application process. The rounded
corners 13 are an advantage for implanted ultra-nanocrystalline
diamond coated devices such as coated integrated circuit 1 because
they eliminate sharp corners and sharp edges that might otherwise
create stress concentrations in the living tissue which could
damage the tissue.
[0045] FIG. 2 provides a cross-sectional view of an integrated
circuit as in FIG. 1, however, the normally electrically insulating
ultra-nanocrystalline diamond 11 has been doped in a selected area
to provide electrically conductive doped ultra-nanocrystalline
diamond electrode 15. This preferred configuration allows the
ultra-nanocrystalline diamond 11 to be completely hermetically
sealed around the silicon substrate 3, thereby protecting the
silicon substrate 3 and electrodes 5 from exposure to living
tissue.
[0046] Obviously, many modifications and variations of the present
invention are possible in light of the above teachings. It is
therefore to be understood that, within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described.
* * * * *